Motor nerve conduction velocity in very preterm infants in relation to L-thyroxine supplementation.
BACKGROUND
Transient hypothyroxinemia is common in preterm infants and has been associated with neurodevelopmental dysfunction and slow nerve conduction velocity. It is still unknown whether L-thyroxine supplementation is required. During an L-thyroxine supplementation trial, motor nerve conduction velocity was measured to answer the question whether L-thyroxine supplementation improves motor nerve conduction velocity.


METHODS
Two hundred infants < 30 weeks' gestational age were enrolled in a randomized, double-blind, placebo-controlled L-thyroxine supplementation trial. L-Thyroxine (8 micrograms/kg birthweight per day) or a placebo was administered during the first 6 weeks of life. Motor nerve conduction velocity was measured in the ulnar and posterior tibial nerve shortly after birth, at 2 weeks, at 40 weeks, and at 66 weeks postmenstrual age.


RESULTS
At 2 weeks, the ulnar motor nerve conduction velocity had improved in the L-thyroxine group compared with the placebo group, although the difference was not statistically significant (difference between means: 0.8 msec; 95% CI: -0.13 to 1.80; p = 0.06). Later on, no effect of L-thyroxine supplementation on motor nerve conduction velocity was found.


CONCLUSIONS
This study shows that in infants < 30 weeks' gestational age L-thyroxine supplementation during the first 6 weeks of life does not clearly improve motor nerve conduction velocity.
Smit
B J
BJ
Academic Medical Center, University of Amsterdam, Emma Children's Hospital AMC Department of Neonatology, The Netherlands.
Kok
J H
JH
de Vries
L S
LS
van Wassenaer
A G
AG
Dekker
F W
FW
Ongerboer de Visser
B W
BW
D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D016014:Linear Models; D008297:Male; D009046:Motor Neurons / Q000187:drug effects*; D009431:Neural Conduction / Q000187:drug effects*; D013974:Thyroxine / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D013979:Tibial Nerve; D014459:Ulnar Nerve
D013974:Thyroxine